“To the great people of West Virginia we have, together, a really great chance to keep making a big difference,” Trump wrote on Monday morning. “Problem is, Don Blankenship, currently running for Senate, can’t win the General Election in your State...No way! Remember Alabama. Vote Rep. Jenkins or A.G. Morrisey!”

Blankenship, a former coal magnate who served a year in prison for his role in a mine disaster that left 29 people dead and is on probation until Wednesday, has drawn the ire of party leadership both for his criminal record and his inflammatory and sometimes racist rhetoric. He faces state Attorney General Patrick Morrisey and Rep. Evan Jenkins in Tuesday’s primary, with the winner taking on Sen. Joe Manchin, D-W.V., in November in what is expected to be a tight race.

Morrisey and Jenkins welcomed Trump’s input.

“.@realDonaldTrump is exactly right,” Morrisey tweeted. “@DonBlankenship would be a disaster for West Virginia and would get trounced by @Sen_JoeManchin. Help Trump and the conservative fighter defeat this convicted criminal.”

“The President is a very busy man and he doesn’t know me, and he doesn’t know how flawed my two main opponents are in this primary,” he said in a statement. “The establishment is misinforming him because they do not want me to be in the U.S. Senate and promote the President’s agenda.”

West Virginia is a key state for Republican efforts to retain control of the Senate and expand their narrow majority. Manchin’s conservative views often frustrate progressive Democrats, but he has opposed several Trump priorities, including his tax cuts, making him highly vulnerable in a state that Trump won by 40 points in 2016.

“We’re a red state. We were the second-strongest state for Trump in the country,” said Democratic strategist Mike Plante, who worked on Manchin’s successful 2004 gubernatorial campaign. “Whoever the nominee is will present challenges, but Joe Manchin has consistently shown in three elections in which the state was trending Republican, he was winning elections in that environment.”

Trump’s tweet comparing Blankenship to failed Alabama Senate candidate Roy Moore reportedly came at the urging of Senate Majority Leader Mitch McConnell. It also echoed arguments made by Trump’s son last week about Blankenship’s unelectability.

"I hate to lose. So I'm gonna go out on a limb here and ask the people of West Virginia to make a wise decision and reject Blankenship! No more fumbles like Alabama," Donald Trump Jr. tweeted.

Noting that similar prediction of certain general election disaster were lodged against Trump during his 2016 primary campaign, West Virginia experts say a Blankenship loss to Manchin is not guaranteed.

“Ironically, the president’s victory in 2016 is why I would never say Don Blankenship doesn’t have a chance,” said Patrick Hickey, a professor of political science at West Virginia University.

However, Blankenship could face a tougher general election battle than Morrisey and Jenkins, particularly among independents and a faction of registered Democrats who tend to vote Republican.

“I think a lot of them are going to have more of an open mind to Jenkins and Morrisey than to Blankenship,” Hickey said.

Manchin will face dissatisfaction from the extreme flank of his own party, where liberals who show up at the polls to vote for progressive candidates in local races might choose a third party Senate candidate over the conservative Democrat.

“If 5 to 10 percent goes to a third candidate in this race, that could be the deciding factor,” Hickey said. “That could be what causes Manchin to lose.”

As McConnell allies fight to keep an unpredictable ex-con off the November ballot, Blankenship has waged an overtly personal campaign against McConnell, or “Cocaine Mitch” as he recently branded him. The nickname is an apparent reference to drugs purportedly found on a ship owned by McConnell’s wife’s family. Blankenship has also taken aim at McConnell’s wife, Transportation Secretary Elaine Chao, and her “Chinaperson” father, though he denied his use of that nomenclature was racist.

“If it were not for the Upper Big Branch mine disaster, I think he would easily win the Republican primary,” Hickey said.

Nobody is sure exactly how Trump’s tweet will play with primary voters, 68,000 of whom had already voted before reading it. After weeks of relentless attack ads from candidates and PACs, his input may not sway them.

“The president’s opinion, does it count for something with West Virginia voters?” Plante said. “Sure, but we’ve got a couple of tweets and some resulting news coverage of it, but then you have millions of dollars of advertising people are getting hit with every day on their TV.”

Trump sided with McConnell against Roy Moore in the Alabama primary last year. Trump threw his support behind Moore after he won the nomination, sticking by him even after much of the party distanced itself when Moore was accused of having engaged in sexual misconduct with teenage girls as a young prosecutor. Moore ultimately lost to Democrat Doug Jones, an outcome the party is desperately trying not to repeat.

According to Hickey, McConnell and Trump may have gotten involved too late to prevent voters from siding with Blankenship, whose behavior has drawn disproportionate media attention.

“They sort of did the worst of both worlds, in that they ignored him for months now and here in the last few days they’re training fire on him…,” he said, drawing another parallel to Trump’s campaign. “Right now, because he’s played the media like a fiddle, like Trump did, that’s allowed him to build up this name recognition and support.”

A victory for Blankenship Tuesday may be taken as evidence of his viability, but Hickey suggested general election voters may be more troubled by his culpability for a fatal mine explosion than GOP primary voters. If Trump and Moore’s campaigns are any indication, he expects much of the Republican establishment would circle around Blankenship, with at least one exception.

“Mitch McConnell’s probably not going to be out there campaigning for him,” he said.